no SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 



Flora of Clifbon Dist»rict», Arizona 



BY A. DAVIDSON, M. D. 

 (Paper read before Section of Botanj' Oct. 18, 1904) 



In due course of time some enterprising botanist will give 

 ns. if not a flora, at least a local list, of the plants of Arizona. 



Arizona possesses probably the most interesting and varied 

 flora of any state in. the Union. Many of its plants are consid- 

 ered rare and local, but this "rarity is probably more apparent 

 than real. The greater part of the country is practically un- 

 known to the naturalist and many years must elapse before the 

 work of exploration is even superficially performed. 



The lack of facilities for travel and accommodation are 

 the least of the difficulties. The climatic conditions are the 

 deterrent factors. Contrary to the usual belief, Arizona is by 

 no means an arid country. The average rainfall, even in the 

 south, is probably at least seven inches and in the north it is 

 more. The greatest precipitation is normally in the summer 

 time, beginning with the 1st of July and ending the end of 

 August, or middle of September. The winter's snow or rain- 

 fall appears in January and December. Thus there are two 

 floras, contingent on the rainfall in spring and autumn. To 

 thoroughly explore any district the same ground would require 

 visiting after each rain, but the summer rains are so unequally 

 distributed that a locality explored one spring might not re- 

 ceive sufficient summer rain for the two or three seasons fol- 

 lowing. 



Last autumn I visited Chase Creek and found it practi- 

 cally destitute of vegetation, while the country ten miles away 

 was a carpet of green. These experiences are common. As 

 you go botanizing in the summer time, with the thermometer 

 around 90 degrees at midnight, you clothe yourself in a silk 

 shirt and a pair of duck trousers and pray for rain, and when 

 it catches you on some rocky slope or treeless plain in the form 

 of a cold, drenching thunderstorm you pray again for warmth. 

 Altogether the conditions are not favorable to good and philo- 

 sophic work. 



As many years are likely to elapse before the country is 

 sufficiently closely explored to give a clear idea of the distribu- 

 tion of its numerous species, any list of plants now published 

 will prove of immense value to future investigators. 



In this number I have begun the publication of the plants 

 secured by me in the neighborhood of Clifton. The district 

 covered extends from the New ^Mexico border near Duncan, 

 twenty-five miles south of Clifton, to the Blue River, a tribu- 

 tary of the Frisco, nearly twenty miles north of Clifton, and 



